This application addresses the problem of longer lasting accurate marks applied to the ocular surface as needed. In the field of refractive surgery there exists a need to place marks on the eye (e.g., ink marks) in order to orient the treatment of astigmatism, among others. In the field of cataract surgery, for example, a corneal astigmatism can be balanced by an intraocular toric lens implant having a curved surface that counterbalances the corneal astigmatism. In such methods for treating astigmatism, the eye should be marked before surgery in order to properly position the treatment of the astigmatism.
Patients undergoing such treatments are ideally required to have the operative site marked with a surgical marker before being brought into the operating room. However, conventional marking devices suffer from issues of, among other things, inadequate ink transfer to the eye surface. Such inadequacy of transfer results principally from the fact that conventional devices are first marked with only a thin layer of wet ink which is then transferred to a wet ocular surface. As a consequence of placing wet ink onto a wet ocular surface, the patient blinks off ink marks from conventional marking devices in a matter of minutes, an undesirably short period of time.
Additionally, it is well known that the eye position rotates or undergoes cyclotorsion when the patient moves from a vertical or sitting position to a lying or horizontal position. The change in position creates an error in marking an eye, and the error can be upwards of 20 degrees, which is clinically significant. As a consequence, the best practice is to mark the patient's eye while the patient is in a vertical or sitting position, because that position is the normal position for use of the eyes. However, this best practice often conflicts with the typical operating room practice of having the patient lying down, prepared for surgery, draped, and ready for the surgeon before the surgeon enters the room. The need to mark the patient in the sitting position delays the normal preparation sequence for surgery.
An alternative practice is to pre-mark a patient in a separate preparation area, in which oral sedation and IVs are generally administered. The pre-marking may be administered with a surgical ink marker pen to the area where the cornea meets the sclera. Such conventional markers leave a lasting dot of ink not found on the thin film of ink applied with conventional sterile metal markers. However the placement of surgical ink marker dots is imprecise and over time the dots tend to smear, creating an undesirable ambiguity of the original intended pinpoint location.
One practice of medicine convention now requires surgeons to mark the patient's brow over the eye having surgery prior to being moved to the operating room. Because every patient gets a correct surgical site identification mark with a surgical marker over the brow, it is convenient for the surgeon to add marks on the eye at the same time. Since conventional metal markers retain only a thin film of ink that is blinked off within minutes, they are not effective for marking outside of the operating room. Consequently, the only lasting marks that can be made before surgery under conventional methods are ink dots placed in the general horizontal and vertical meridians. As noted above, these hand placed dots are not precise and tend to smear over time.
For all the above reasons, the conventional systems for marking the eye for treatment of astigmatism is complex, and suffers from limitations with respect to at least the accuracy of the marks placed, how the procedure is performed, and how the patient is prepared for surgery.
Prior corneal marking devices generally depend on an external source of gentian violet (“GV”) ink. In most cases, the GV ink is provided from a sterile GV felt tip pen commonly used to mark the surgical site of patients undergoing various surgeries. The GV ink contained in these pens is generally either a 98% aqueous solution containing 2% GV or a similar aqueous solution of GV with a very small amount of an alcohol solution. Such solutions have long been used with markers for the skin surface but were never intended for use of the relatively sharp edges of a corneal marker.
U.S. Pat. No. 9,283,117, which is fully incorporated herein by reference, describes improved eye marker devices overcoming the shortfalls of the conventional devices and systems for marking the eye for treatment of astigmatism. Such application discloses, among other things, an improved marker device with sharp edges made of various types of material. When the mostly aqueous solution is applied to a metal edge of a corneal marker, the surface tension and surface energy is such that the GV ink tends to bead-up on the marker edge. The conventional mostly aqueous GV on the marker tip is then applied to the cornea. The corneal surface, however, is covered with a tear film composed of 3 separate layers, principally oil, water and mucous. Consequently, a principally aqueous GV layer on the marker tip goes into solution as the tip traverses the 3 layers of the tear film. Only the ink that survives the transit through the tear film can reach the corneal epithelium where vital staining actually occurs. Because this traditional technique uses a wet GV ink to mark a wet cornea, it has been common to see that the marks so placed are generally smeared and easily blinked off, undesirably limiting the duration of visibility of the marks. Limited duration of corneal ink marks places serious constraints on the timing of preoperative corneal marks because the patient must be marked relatively close to the time of eye surgery for the marks to still be visible for use during surgery. These time constraints then interfere with the best patient flow and efficiency for the patients, surgeon, and surgery center. Additionally, if the ink marks are smeared, ill defined, or faint, the final visual result for the patient can be compromised because the surgeon cannot accurately align the treatment of the patient's astigmatism.
For the sake of good patient treatment, and the need for better operating center efficiencies, alternative methods and associated marking inks and devices are needed. Although a primarily wet alcohol-based GV ink formula could overcome some of the issues of wet ink on a wet cornea, it is well known that alcohols are toxic to the corneal epithelium and as such are not favored. Additionally, current 2% GV aqueous based solutions can be applied to a marker tip and left to dry, but the coverage of the marker may be irregular as noted above because of the surface tension and surface energy problems of water on a non-porous edge such as the traditional metal of reusable metal corneal markers. Even non-metallic materials behave similarly with irregular coverage for the same reasons. Further, because of the relatively low concentration of GV molecules in solution that can be located on the marker edge (in view of the limitations discussed above), the ink marks once again suffer from limited longevity. For at least these reasons, improvements in eye marking ink are desired.
In the fields of femtosecond cataract surgery and corneal cross linking, most treatment devices use an infrared camera to visualize the eye. The standard ink used by eye surgeons for marking the eye is GV ink but this ink is invisible under infrared cameras used by a majority of treatment devices. While the ink in a Sharpie™ type marker is visible under the treatment devices' infrared cameras, this ink is not FDA approved. The formula is based on “polychrome” with a quickly evaporating vehicle, both of which have no data concerning safety for use on the ocular surface. Moreover, this unapproved ink has to be placed on the eye with a wet ink marker because the dried ink is adherent to metal or plastic corneal marker tips and will not transfer to the cornea. Accordingly, there exists a need to provide eye surgeons with an infrared visible ink having a known safety profile.